Online measurement of fluid reabsorption in renal tubules

Malnic, Gerhard; Netto, Cincinato Rodrigues Silva; Stamopoulos, C. D.; Aires, Margarida de Mello

doi:10.1007/bf02443818

Cited by 5 publications

(3 citation statements)

References 7 publications

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“…Therefore, these results clearly show that the natriuresis induced by intrahypothalamic injection of carbachol is independent of the alterations in renal efferent nerve activity. It is likely that other factors, including OT and/or ANP effects, are involved in the efferent renal nerve activity (324,478).…”

Section: Role Of ␣-Adrenergic and Cholinergic Receptors In Controlmentioning

confidence: 99%

Neuroendocrine Control of Body Fluid Metabolism

Antunes‐Rodrigues

Castro

Elias

et al. 2004

Physiological Reviews

401

310

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Mammals control the volume and osmolality of their body fluids from stimuli that arise from both the intracellular and extracellular fluid compartments. These stimuli are sensed by two kinds of receptors: osmoreceptor-Na+ receptors and volume or pressure receptors. This information is conveyed to specific areas of the central nervous system responsible for an integrated response, which depends on the integrity of the anteroventral region of the third ventricle, e.g., organum vasculosum of the lamina terminalis, median preoptic nucleus, and subfornical organ. The hypothalamo-neurohypophysial system plays a fundamental role in the maintenance of body fluid homeostasis by secreting vasopressin and oxytocin in response to osmotic and nonosmotic stimuli. Since the discovery of the atrial natriuretic peptide (ANP), a large number of publications have demonstrated that this peptide provides a potent defense mechanism against volume overload in mammals, including humans. ANP is mostly localized in the heart, but ANP and its receptor are also found in hypothalamic and brain stem areas involved in body fluid volume and blood pressure regulation. Blood volume expansion acts not only directly on the heart, by stretch of atrial myocytes to increase the release of ANP, but also on the brain ANPergic neurons through afferent inputs from baroreceptors. Angiotensin II also plays an important role in the regulation of body fluids, being a potent inducer of thirst and, in general, antagonizes the actions of ANP. This review emphasizes the role played by brain ANP and its interaction with neurohypophysial hormones in the control of body fluid homeostasis.

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Section: Role Of ␣-Adrenergic and Cholinergic Receptors In Controlmentioning

confidence: 99%

Neuroendocrine Control of Body Fluid Metabolism

Antunes‐Rodrigues

Castro

Elias

et al. 2004

Physiological Reviews

401

310

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“…In the second series, a peritubular capillary was perfused with single barrel micropipcttes containing mammalian bicarbonate Rin ger's solution without or with \0~i M (±(verapamil applying pressure of l.5kg/cm2 to the micropipette, while tubules were perfused as described above, with isotonic saline. Fluid reabsorption in proximal tubules was measured by the technique ofdcrt: [15] as modified in our laboratory [16]. The meniscus effect was cor rected according to (ivory [17].…”

Section: Micropuncture Experimentsmentioning

confidence: 99%

Verapamil Effect on Renal Function of Normotensive and Hypertensive Rats

MacLaughlin¹,

Aires²,

Malnic³

1985

Kidney Blood Press Res

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The effect of verapamil, a Ca⁺⁺ antagonist drug, on renal function and proximal fluid reabsorption in normal and hypertensive (GΠ) rats was studied. During intravenous infusion of verapamil, mean arterial pressure (MAP) fell significantly in both groups, 23% more in hypertensive than in normotensive rats. Glomerular filtration rate (GFR) was significantly higher in hypertensive rats and also increased significantly in this group during verapamil infusion. Effective renal plasma flow (ERPF) was similar in both groups and did not change significantly during verapamil infusion. The increase in urine flow, Na⁺ and Ca⁺⁺ excretion was higher in hypertensive than in normotensive rats during verapamil infusion. When 10^-5M verapamil was added to the luminal perfusate of proximal tubules, fluid reabsorption was reduced to 64% in normotensive and to 42% in hypertensive rats. When added to capillary perfusate, fluid reabsorption was almost completely but reversibly inhibited (92% in normotensive and 83% in hypertensive rats). Our findings indicate a direct effect of verapamil on renal Na⁺ and possibly also on Ca⁺⁺ reabsorption, suggesting involvement of the Na⁺-Ca⁺⁺ countertransport system. The greater effect of verapamil on Na⁺ excretion in hypertensive rats was not due to increased action on proximal Na⁺ reabsorption.

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“…Changes in volume of a luminal fluid column were measured by a modification of the Gertz splitdroplet method (Malnic. Silva Neto.…”

Section: Methodsmentioning

confidence: 99%

Effect of medium tonicity on transepithelial H(+)‐HCO3‐fluxes in rat proximal tubule.

Melis

Malnic

Aires

1993

The Journal of Physiology

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SUMMARY1. The effect of luminal and capillary perfusion with hypotonic or hypertonic solutions containing 25 mm NaHC(3 or NaH2PO4 plus NaCl, K+, Ca2+, Mg2+ and acetate at an osmolalitv of 100 or 500 mosmol kg-1 on rat proximal ll+ secretion was estimated by monitoring luminal pH with Sb microelectrodes. The results were compared to perfusions with the same ionic concentration in which tonicity was adjusted to 300 mosinol kg-1 with raffinose.2. The kinetics of acidification of luminally injected bicarbonate buffer permits evaluations of H+-HCO3-fluxes as well as stationary pH gradients; the kinetics of alkalinization of luminally injected acid phosphate buffer indicates HI-HCO3-backfluxes from blood to lumen.3. In alkalinization experiments, luminal perfusion with hypotonic solution during presence of blood in capillaries or hypotonic capillary perfusion leads to a decrease of stationary pH. an increase of alkalinization half-time and consequently a decrease of passive H+-HCO3-backflux.4. In alkalinization experiments, during luminal and/or capillary perfusions with hypertonic solutions, no significant differences in the stationary pH, alkalinization half-time and H+-HC03-backflux were found.5. During acidification experiments, with both hypo and hypertonic perfusions: no significant differences in stationary pH, acidification half-time and H+-IHCO3 flux were observed.

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Online measurement of fluid reabsorption in renal tubules

Cited by 5 publications

References 7 publications

Neuroendocrine Control of Body Fluid Metabolism

Neuroendocrine Control of Body Fluid Metabolism

Verapamil Effect on Renal Function of Normotensive and Hypertensive Rats

Effect of medium tonicity on transepithelial H(+)‐HCO3‐fluxes in rat proximal tubule.

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